1. Field of the Invention
The present invention relates to a magnetic recording/reproduction apparatus.
2. Description of the Related Art
Referring to FIGS. 36 to 38, a conventional magnetic recording/reproduction apparatus 300 will be described.
The magnetic recording/reproduction apparatus 300 includes a main chassis 308 and a sub-chassis 303 which can slide relative to the main chassis 308 in the direction indicated by arrow A. An S reel base 304 is swingably mounted on the sub-chassis 303 and adapted to engage with a reel hub (not shown) of a cassette 301.
A tension arm 312 having a tension post 314 is swingably mounted on the sub-chassis 303 and swung by a driving source (not shown) to draw out a tape 302. An S boat 339 having an S1 post 345 and an S2 post 344 extending therefrom is mounted on the main chassis 308. The S boat 339 moves from a position inside a cassette mouth (the position shown in FIG. 36) to a position in the vicinity of a cylinder 338, so that the tape 302 is drawn out from the cassette 301 and passes around the cylinder 338 for a predetermined arc.
A tape loading operation of the above conventional apparatus will be described.
FIG. 36 illustrates the state in which the cassette 301 can be placed on the sub-chassis 303 (UNLOADED state). In this state, the tension post 314 is located in the cassette mouth. From this state, members such as the sub-chassis 303, the tension post 314, and the S boat 339 move to the position shown in FIG. 37 at which the tape 302 has been drawn out to pass around the cylinder 338. FIG. 37 illustrates the state in which the tape 302 runs in the forward direction (indicated by arrow A) during recording/reproduction and the like, while FIG. 38 illustrates the state in which the tape 302 runs in the backward direction (indicated by arrow B) during reverse reproduction and the like.
The construction and operation of the tension control mechanism will be described.
The tension arm 312 is swingably mounted on the sub-chassis 303, and driven by an tension arm regulating pin 313, to move between the position shown in FIG. 37 and the position shown in FIG. 38, so that the tension post 314 extending from the top of the tension arm 312 guides the tape 302 and simultaneously controls the tension of the tape 302.
One end 319B of a tension band 319 is fixed to the sub-chassis 303, while the other end 320 thereof is swingably attached to the tension arm 312. The center portion of the tension band 319 is passed around a cylinder portion 326 formed around the circumferences of the S reel base 304. A tension spring 327 extends between the tension arm 312 and the sub-chassis 303.
In the above configuration, consider the case where the tape 302 runs in the forward direction for recording/reproduction in the state shown in FIG. 37. Since the tension band 319 is tensioned around the cylinder portion 326 for a predetermined arc, a friction force is generated between the tension band 319 and the cylinder portion 326. At this time, since the tape 302 is tensioned around the tension post 314 when it runs, the friction force is subjected to feedback, whereby the tape tension is kept stabilized.
In the case where the tape 302 runs in the backward direction, the tension arm regulating pin 313 is driven and positioned by a driving member (not shown), which in turn swings and positions the tension arm 312 to the position shown in FIG. 38. At this time, the tension band 319 is loosened from the cylinder portion 326 as represented by the reference numeral 319C, allowing the S reel base 304 to be released from load and thus the tape 302 to be released from tension. In this way, since the S reel base 304 becomes rotatable free from a force by the tension band 319, the tape 302 which has run in the direction B can be wound onto a reel on the S reel base 304. In FIGS. 36 to 38, a driving means for rotating the S reel base 304 is not shown.
In the unloaded position shown in FIG. 36, the tension post 314 is located inside the cassette mouth. In this state, since the end 320 of the tension band 319 is located in the vicinity of the S reel base 304, the tension band 319 has loosened from the cylinder portion 326 as represented by the reference numeral 319A. This loosening is greater than the loosening (319C) shown in FIG. 38.
FIG. 39 is a side sectional view of the S reel base 304 and the tension band 319 in the state shown in FIG. 37. In FIG. 39, the tension band 319 and the cylinder portion 326 are shown as if they are apart from each other for convenience.
In the above configuration, however, the following problem arises.
First, in the unloaded state shown in FIG. 36, the tension band 319 is loosened so much (as represented by 319A) that it is too far away from the cylinder portion 326 of the S reel base 304, as represented by the reference numerals 319D and 319E shown in FIG. 40. When the apparatus is shifted from this state to the state shown in FIG. 37, the tension band 319 may sometimes fail to be passed around the cylinder portion 326 at a proper height (shown in FIG. 39) with respect to the cylinder portion 326. If the running of the tape 302 is executed in this state, the tape 302 will not have a normal tension, which not only prevents recording/reproduction but also causes tape damage.
In order to avoid the above problem, a large flange as shown by the reference numeral 304B in FIG. 40 is formed on the S reel base 304. Such a large flange can prevent the tension band 319 from displacing from the cylinder portion 326. However, a large flange is required to keep the tension band 319 from displacing from the flange when the tension band 319 is loosened at a maximum. This blocks realization of a small-size mechanism.
Secondly, as shown in FIG. 38, when the tape 302 runs in the reverse direction, the tension post 314 moves from a position 314A (normal position) to a position 314B. The run path of the tape 302 is therefore displaced from the tape path established when the tape 302 runs in the forward direction. Since the tape path in the forward direction is designed as an ideal tape path, tape damage may possibly occur when the tape runs along the tape path displaced from the ideal tape path. In order to avoid this problem, it is required to finely control the tension applied to the tape during running and strictly ensure the tilt precision and the positional precision of the posts. This also blocks realization of a small-size mechanism.
Moreover, since the position of the tension post 314 moves in the wide range between the positions 314A and 314B among the states, other members are not allowed to be placed in this range. This again blocks realization of a small-size mechanism.
The object of the present invention is to provide a magnetic recording/reproduction apparatus including a small and highly reliable mechanism in which the tension band 319 is prevented from slacking in the unloaded state and is passed around a cylinder portion 326 properly when the tape runs in the forward direction at a recording rate for recording/reproduction, so that a proper tension can be applied to the tape, and the position of the tension post 314 is not displaced from an ideal tape path when the tape 302 runs for operations other than the recording/reproduction or when the tape 302 does not run.